1. Field of the Invention
This invention relates to a position detecting signal generator.
2. Description of the Prior Art
FIG. 1 shows a conventional rotation detecting apparatus, for example, for a rotary drum of a video tape recorder. Generally, such rotation detecting apparatus requires a frequency generator (FG) for control of rotational speed, and a pulse generator (PG) for detecting the rotary phase of the magnetic head. In FIG. 1, the frequency generator is constituted by an FG detecting head 1 and a plurality of magnet pieces 3 fixed on a rotary drum 2 in opposing or facing relation to FG detecting head 1. The pulse generator is constituted by a detecting head 4 and one magnet piece 5 in opposing relation thereto. The outputs of the detecting heads in FIG. 1 are shown in FIG. 2, FIG. 2A showing the PG output of PG detecting head 4, and FIG. 2B showing the FG output of FG detecting head 1.
Thus, two rotation control systems for the FG and PG outputs must be provided in the electronic circuitry. Accordingly, the number of circuit parts becomes large. In addition, the electronic apparatus becomes expensive, and it becomes difficult to make it in a small size. Further, when the rotational position of the rotating body is exactly detected from the rotational position detection signal of FIG. 2A, a zero cross-over point Z must be found, resulting in further complication of the circuit.
A magnetic detecting head is also used in the rotation detecting apparatus of FIG. 1. It is also possible to use a photo-interrupter (light intercepting type) or a photo reflector (light reflecting type) to produce the PG and FG signals in a recording/reproducing apparatus using a floppy disc. However, this apparatus also has the above-described defects.